Whom is correct in both blanks but who would be fine too. As others have said, people just don't use whom that often these days, even in formal writing. It can sound sort of cold or pedantic. There is one case where whom is required and who would definitely be wrong: preposition + whom. For example, some people don't want to end a sentence with a preposition so they would rewrite #1 as: She is one of the best people FOR WHOM I have ever worked. In this case you must use whom -- it's not optional and who would be wrong. You could also leave both items blank. You can always omit the relative pronoun in object relative clauses. "That" is correct in everyday conversation but not in writing.

1) It's a person, so your choices are limited to "who/whom". The answer is "who" because "she" is the subject of the sentence ("Who is she?") Personally, I'd leave it blank. However, if your only choices allowed are "who" and "whom", then use "who". 2) I agree with you here. You met the professor, so "whom" should apply. I double-checked this one, but I'm curious if any other member has a proper explanation for "who". http://www.ego4u.com/en/cram-up/grammar/relative-clauses

I assume the so-called "my answers" is just your hypothesis, there weren't the alt options, were there? Yes, that, whom, and NWAB are all perfectly fit in the brackets, too. The only reason why "who" is chosen to be right answer (as the original sentences put, not actually choice questions, I guess) is, langauges develop. Because everyone accepts it, it's then accepted. As a matter of fact, most natives now even can't be very sure of the use of the word "whom", themselves, including the well educated. Just do a poll or something here. Funny enough, I thought according to the strictest Chinese-based English grammar rules, the right answer for the first sentence would then def be --- "that", because of the "one of the best" structure thing. Of course, you probably wouldn't've heard of it, as the majority of human beings on earth have not.

是的，是填空题，不是选择题~~

Please elaborate yourself, Miss April >>> having blank to fill in, not type of the option question <<< I didn't mean you changed the sentence, I was just saying they CANNOT be "option questions", so it was just like, a blank to fill in whatever you want to write there? Like, 填空题，而不是选择题, yes? No other options listed, are there?